Short packet for use in beamforming

ABSTRACT

A method for generating a beamforming training (BFT) unit includes generating a physical layer (PHY) preamble of the BFT unit and generating a first encoding block and a second encoding block using PHY data and MAC data, including at least one of i) using a number of padding bits in a PHY layer of the BFT unit such that the BFT unit consists of the PHY preamble, the first encoding block, and the second encoding block, and ii) generating a MAC protocol data unit (MPDU) having a length such that the BFT unit consists of the PHY preamble, the first encoding block, and the second encoding block.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/876,758, entitled “Short Packet for Use in Beamforming,” filed Sep.7, 2010, which claims the benefit of U.S. Provisional Patent ApplicationNo. 61/243,848, entitled “Tx Sector Sweep for 60 GHz,” filed Sep. 18,2009. The entire disclosures of both applications above are herebyexpressly incorporated herein by reference.

FIELD OF TECHNOLOGY

The present disclosure relates generally to communication systems and,more particularly, to information formats for exchanging information viacommunication channels.

BACKGROUND

An ever-increasing number of relatively inexpensive, low power wirelessdata communication services, networks and devices have been madeavailable over the past number of years, promising near wire speedtransmission and reliability. Various wireless technology is describedin detail in several IEEE standards documents, including for example,the IEEE Standard 802.11b (1999) and its updates and amendments, as wellas the IEEE 802.15.3 Draft Standard (2003) and the IEEE 802.15.3c DraftD0.0 Standard, all of which are collectively incorporated herein fullyby reference.

As one example, a type of a wireless network known as a wirelesspersonal area network (WPAN) involves the interconnection of devicesthat are typically, but not necessarily, physically located closertogether than wireless local area networks (WLANs) such as WLANs thatconform to the IEEE Standard 802.11a. Recently, the interest and demandfor particularly high data rates (e.g., in excess of 1 Gbps) in suchnetworks has significantly increased. One approach to realizing highdata rates in a WPAN is to use hundreds of MHz, or even several GHz, ofbandwidth. For example, the unlicensed 60 GHz band provides one suchpossible range of operation.

In general, transmission systems compliant with the IEEE 802.15nstandards support one or both of a Single Carrier (SC) mode of operationand an Orthogonal Frequency Division Multiplexing (OFDM) mode ofoperation to achieve higher data transmission rates. For example, asimple, low-power handheld device may operate only in the SC mode, amore complex device that supports a longer range of operation mayoperate only in the OFDM mode, and some dual-mode devices may switchbetween SC and OFDM modes. Additionally, devices operating in suchsystems may support a control mode of operation at the physical layer ofthe protocol stack, referred to herein as “control PHY.” Generallyspeaking, control PHY of a transmission system corresponds to the lowestdata rate supported by each of the devices operating in the transmissionsystem. Devices may transmit and receive control PHY frames tocommunicate basic control information such as beacon data or beamformingdata, for example.

The IEEE 802.15.3c Draft D0.0 Standard is directed to wireless widebandcommunication systems that operate in the 60 GHz band. In general,antennas and, accordingly, associated effective wireless channels arehighly directional at frequencies near or above 60 GHz. When multipleantennas are available at a transmitter, a receiver, or both, it istherefore important to apply efficient beam patterns to the antennas tobetter exploit spatial selectivity of the corresponding wirelesschannel. Generally speaking, beamforming or beamsteering creates aspatial gain pattern having one or more high gain lobes or beams (ascompared to the gain obtained by an omni-directional antenna) in one ormore particular directions, with reduced the gain in other directions.If the gain pattern for multiple transmit antennas, for example, isconfigured to produce a high gain lobe in the direction of a receiver,better transmission reliability can be obtained over that obtained withan omni-directional transmission.

Beamforming generally involves controlling the phase and/or amplitude ofa signal at each of a plurality of antennas to define a radiation orgain pattern. The set of amplitudes/phases applied to a plurality ofantennas to perform beamforming is often referred to as a steeringvector (or “phasor”). The IEEE 802.15.3c Draft D0.0 Standard proposes amethod for selecting a steering vector. For selecting a transmitsteering vector, the proposed method generally involves, for example,transmitting training signals during a training period using each of aplurality of steering vectors, determining the quality of the receivedtraining signals, and selecting a steering vector that corresponds tothe “best” received training signal. Thus, generally speaking,beamforming requires an exchange of beamforming training data betweencommunication devices. This data takes up a large portion of theavailable bandwidth, resulting in a lower data throughput.

SUMMARY

In an embodiment, a method for generating a beamforming training (BFT)unit includes generating a physical layer (PHY) preamble of the BFT unitand generating a first encoding block and a second encoding block usingPHY data and MAC data, including at least one of i) using a number ofpadding bits in a PHY layer of the BFT unit such that the BFT unitconsists of the PHY preamble, the first encoding block, and the secondencoding block, and ii) generating a MAC protocol data unit (MPDU)having a length such that the BFT unit consists of the PHY preamble, thefirst encoding block, and the second encoding block.

In an embodiment, an apparatus includes a block encoder to generateencoding blocks of a predetermined length, a beamforming training (BFT)unit generator communicatively coupled to the block encoder, the BFTunit generator to generate a BFT unit that consists of i) a physicallayer (PHY) preamble and ii) data encoded in two encoding blocks, whereBFT unit generator is configured to perform at least one of: i) cause aPHY generator to use a number of padding bits in the BFT unit such thatthe data is encoded in exactly two encoding blocks; and ii) cause aMedia Access Control (MAC) generator to generate a MAC protocol dataunit (MPDU) having a length such that the data is encoded in exactly twoencoding blocks.

In an embodiment, in a wireless communication system, a method forgenerating a beamforming training (BFT) unit includes encoding data asan integer number of encoding blocks, where each of the integer numberof encoding blocks includes a respective portion of the data andrespective check bits, and exactly one of the integer number of encodingblocks includes padding bits.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a communication system in which devicestransmit beamforming data using the efficient formats of the presentdisclosure;

FIG. 2 is a diagram of an encoding block used in transmitting data unitsin the communication system of FIG. 1, according to an embodiment;

FIG. 3A is a diagram of a prior art beamforming training (BFT) unit;

FIG. 3B is a diagram of a prior art MAC protocol data unit (MPDU) usedin a BFT unit;

FIG. 3C is a diagram of a prior art transmit sector sweep (Tx SS)information element (IE) used in a BFT unit;

FIG. 3D is a diagram of a prior art frame control field used in a BFTunit;

FIG. 4 is a diagram of a BFT unit efficiently formatted according to anembodiment of the present disclosure;

FIG. 5A is a diagram of an efficiently formatted MPDU of a BFT unit,according to an embodiment;

FIG. 5B is a diagram of an efficiently formatted MPDU of a BFT unit,according to another embodiment;

FIG. 5C is a diagram of an efficiently formatted MPDU of a BFT unit,according to yet another embodiment;

FIG. 6A is a diagram of an efficiently formatted sector sweep field,according to an embodiment;

FIG. 6B is a diagram of an efficiently formatted sector sweep field,according to another embodiment;

FIG. 6C is a diagram of an efficiently formatted sector sweep field,according to yet another embodiment;

FIG. 7A is diagram of an efficiently formatted frame control field,according to an embodiment;

FIG. 7B is diagram of an efficiently formatted frame control field,according to another embodiment; and

FIG. 8 is a block diagram of a beamforming controller that implementsone or several formatting techniques of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates a wireless communication system 10 in which a pair ofcommunicating devices, such as a station 12 and a piconet central point(PCP) 14, format beamforming training (BFT) units (e.g., packets,frames) so as to reduce the overhead associated with transmittingbeamforming information over a shared wireless communication channel 16.In an embodiment, the station 12 and the PCP 14 exchange BFT units thatoccupy only two encoding blocks. Each encoding block is generated usinglow-density parity check (LDPC) coding or another technique forgenerating an error-correcting code (ECC), according to an embodiment.

During beamforming training, devices operating in the wirelesscommunication system 10 modulate BFT units using the lowest data rate soas to enable any device to properly receive the BFT units, according tosome embodiments. For example, in an embodiment, the communicationsystem 10 includes single carrier (SC) only, orthogonal frequencydivision multiplexing (OFDM) only, or dual-mode (SC and OFDM) devices,and modulation of BFT units accordingly is selected to match the slowestsupported data rate (i.e., SC). To improve network efficiency, it isparticularly beneficial for communicating devices to reduce the durationof BFT units and other data units (e.g., control PHY units) transmittedat the slowest data rate.

The devices 12 and 14 are equipped with respective sets of one or moreantennas 20-24 and 30-34. In general, devices in the wirelesscommunication system 10 operate in multiple modes (e.g., a transmit modeand a receive mode). Accordingly, in some embodiments, antennas 20-24and 30-34 support both transmission and reception. However, in otherembodiments, a given device includes separate transmit antennas andseparate receive antennas. Further, although the example wirelesscommunication system 10 illustrated in FIG. 1 includes two devices, 12and 14, each with three antennas, the wireless communication system 10in general can include any number of devices, each equipped with thesame or a different number of antennas (e.g., 1, 2, 3, 4 antennas and soon). For beamforming, however, at least one of the devices 12, 14generally should include more than one antenna.

In an embodiment, each of the devices 12 and 14 includes an efficientbeamforming (BF) controller 18 and 19, respectively, configured togenerate and/or process BFT units that conform to at least one of theformats discussed herein. In some embodiments, the BF controllers 18 and19 support a multi-stage transmit (Tx) beamforming procedure thatincludes a “coarse” sector sweeping stage to identify a (typically wide)sector in which a signal from the transmitting device (e.g., the station12) generates the highest power, and a beam “refinement” stage duringwhich the identified sector is partitioned into multiple smallersub-sectors to identify a more specific direction in which the antennaarray of the transmitting device should be steered to maximize receivepower, reduce interference, or otherwise improve reception. The BFcontrollers 18 and 19 similarly support receive (Rx) multi-stage receivebeamforming to determine a direction in which the antenna array of thereceiving device should be steered to maximize receive power, accordingto an embodiment. In an embodiment, the devices 12 and 14 can furtherrefine sector sweeping or beam refinement during as many stages asdesired. On the other hand, in some embodiments of the wirelesscommunication system 10, the devices 12 and 14 implement only one stageof beamforming (e.g., sector sweeping).

To ensure that a receiver of a BFT unit can properly detect and correctat least some of the errors introduced into the BFT unit duringtransmission over the wireless communication channel 16, the devices 12and 14 utilize error correction techniques such as LDPC encoding. Ingeneral, encoding generates a set of check (or “parity”) bits based on aset of message (or “data”) bits, so that an encoding block includes boththe data bits and the check bits. Upon receiving the encoding block, thereceiving device uses the check bits to ensure the integrity of themessage bits and correct the message bits, if necessary. To efficientlyuse the available bandwidth, the BF controllers 18 and 19 generate BFTunits that include a small number of encoding blocks. In an embodiment,the BF controllers 18 and 19 generate BFT units that consist of only apreamble and two encoding blocks.

In an embodiment, beamforming data in a BFT unit is encoded as anencoding block 40 illustrated in FIG. 2. The encoding block 40 of lengthL, measured in bits, includes N data bits that carry non-redundantinformation (such PHY header data, MAC header data, MAC payload data,etc.) in a portion 42, P padding (or “stuff”) bits in a portion 44, andS check bits in a portion 46. When LDPC or a similar encoding techniqueis used, each encoding block included in a BFT unit is of the same fixedlength L and includes the same fixed number of check bits S. Thus, oneor several padding bits are used to bring the number of bits to beencoded to N−S, when necessary. In other situations, the encoding block40 does not include padding bits (i.e., P=0).

In an embodiment, each of the padding bits is set to zero. In anotherembodiment, each of the padding bits is set to one. Further, dependingon the embodiment, the padding bits are inserted before the portion 42or after the portion 42.

The coding rate R of the encoding block 40 is defined as the ratio ofthe number of non-check bits to the total number of bits in the encodingblock 40. Thus,R=N+P/L  (Eq. 1)Further, the effective coding rate can be defined as the ratio of thenumber of data bits to the sum of data bits and check bits in theencoding block 40R=N/N+S  (Eq. 2)In general, higher code rates are associated with lower reliability oftransmission. In other words, the more check bits are included in anencoding block of fixed length L, the easier it is for the receivingdevice to detect and correct errors in the data bits. Further, for acertain code rate, higher effective code rates are associated with lowerreliability of transmission. Thus, the more zero-padding bits areincluded in an encoding block, the more confidence the receiving devicehas in the N data bits extracted from the encoding block 40 of length L.

A prior art technique for formatting a BFT unit, for use as a sectorsweep frame, a sector sweep feedback frame, or a sector sweepacknowledgment frame, is discussed next with reference to FIGS. 3A-D.

FIG. 3A is a diagram of a prior art BFT unit 50 that includes a PHYpreamble 52 and Physical Layer Convergence Procedure (PLCP) protocollayer data unit (PPDU) 54. As is known, the PHY preamble 52 providestraining information that helps the receiver detect the PPDU 54, adjustan automatic gain control (AGC) setting, obtain frequency and timingsynchronization, etc. The PPDU 54 includes a PHY header 56 thatspecifies basic PHY parameters required for decoding the payload of thePPDU 54 (e.g. the length of the payload, modulation/coding method, pilotinsertion information, etc.) followed by a MAC protocol data unit (MPDU)58 defining the payload of the PPDU 54.

As illustrated in FIG. 3A, the prior art BFT frame 50 includes threeLDPC encoding blocks B1, B2, and B3, each of length L. In accordancewith a certain known protocol specification, L=336 and R=½. The encodingblock B1 includes 36 PHY header bits, first 52 bits of the MPDU 58, 80padding bits in a padding bits portion 60, and 168 bits in a check bitsportion 62. Further, the encoding block B2 includes the next 168 bits ofthe MPDU 58 and the corresponding 168 check bits, and the encoding blockB3 includes the remaining bits of the MPDU 58, the necessary number ofpadding bits, and 168 check bits. It is noted that because the encodingblock B1 includes only 52 bits of the MPDU 58, the remaining bits of theMPDU 58 cannot fit into the encoding block B2 to comply with the codingrate R=½, and a third encoding block is required to accommodate theremainder of the MPDU 58. Thus, the prior art BFT frame 50 includesthree LDPC encoding blocks of length 336 bits, each associated with thecoding rate R=½.

Referring to FIG. 3B, a prior art MPDU 70 includes a frame control field71, a duration field 72, a receiver address field 73, a transmitteraddress field 74, a transmit (Tx) sector sweep (SS) information element(IE) 75, and a frame control field 76. In FIG. 3B, the length of eachinformation element is listed in bit octets.

FIG. 3C is a diagram of a prior art Tx SS IE 80 that includes an elementidentifier 81, a length field 82, a direction field 83, a countdown(CDOWN) field 84 to indicate the number of BFT frames to the end of thecorresponding timeslot or beamforming training session, for example, asector id field 85, a forward sector select field 86, a sector sweeplimit (SLIMIT) field 87 to indicate an upper limit to a number of Tx SSBFT units that can be transmitted, an L-TX field 88 to specify a numberof the beamforming training sequences for Tx sector sweeping, a feedbackrequest (F-BACK REQ) field 89 to request sector sweep feedback, an L-RXfield 90 to specify a number of the beamforming training sequences forreceive (Rx) sector sweeping, a signal-to-noise (SNR) report field 91 toprovide a sector sweep metric, and a reserved field 92. In FIG. 3C, thelength of each information element is listed in bits. It is noted thatsome of the elements in prior art Tx SS IE 80 are used to carryinformation in a one direction (e.g., station to PCP), while otherelements are used to carry information in the opposite direction (e.g.,PCP to station).

FIG. 3D is a diagram of a prior art frame control field 100, used in theprior art BFT frame such as the frame 50, that includes a protocolversion field 101 to specify a protocol version, a type field 102 and asub-type field 103 to specify whether the frame is a management frame ora control frame, for example, a “to distribution system” (ToDS) field104 and a “from distribution system” (FromDS) field 105 to indicate adirection of the frame, a more fragments field 106 to indicate that morefragments associated with the frame are to follow, a retry field 107 tospecify whether the frame corresponds to a retransmission of apreviously transmitted frame, a power management field 108 to indicate apower management mode of the device transmitting the frame, a more datafield 109 to indicate that more frames have been buffered fortransmission, a Wired Equivalent Privacy (WEP) field 110 to indicatewhether the frame body is encrypted, and an order field 111 to indicatethe frame ordering technique being used. Similar to FIG. 3C, the lengthof each information element in FIG. 3D is listed in bits.

Several techniques for generating efficient BFT units are discussednext. In particular, a technique for generating a BFT unit in which thedata portion is encoded in exactly two encoding blocks using a reducedset of padding bits is discussed with reference to FIG. 4. Severaltechniques for efficiently formatting the MPDU of a BFT unit so as toreduce the size of the MPDU are discussed with reference to FIGS. 5A-C.Next, a technique for efficiently formatting an SS IE for use in a BFTunit is discussed with reference to FIGS. 6A-B, and a technique forefficiently formatting a frame control field for use in a BFT unit isdiscussed with reference to FIGS. 7A-B.

First referring to FIG. 4, a BFT unit 120 consists of a preamble 122 andtwo encoding blocks, B1 and B2, of length L, generated using LDPC or asimilar forward error correction (FEC) technique. In an embodiment,L=336 bits. The BFT unit 120 carries an entire prior art MPDU (e.g., theMPDU 70), according to an embodiment. In another embodiment, the BFTunit 120 carries an efficiently formatted MPDU that is shorter than aprior art MPDU.

In an embodiment, the first encoding block B1 includes 36 bits in a PHYheader portion 124, a relatively large number N_(L) of data bits in aMPDU bits portion 126-1, a relatively small number P_(S) of padding bitsin a padding bits portion 128, and S check bits in a check bit portion130. The second encoding block B2 includes the rest of the MPDU bits ina MPDU bits portion 126-2, and S check bits in a check bit portion 132.According to this embodiment, the BFT unit 120 does not include a thirdencoding block. In some embodiments, N_(L) is greater than or equal to68 if the MPDU occupies 29 bytes, and greater than or equal to 72 if theMPDU occupies 30 bytes.

For example, to efficiently transmit a 30-byte MPDU, the parametersN_(L)=72 bits, P_(S)=60, and S=168 are used in the encoding block B1 todefine the effective coding rate of (72+36)/(72+36+168)=0.39, and theparameters N_(L)=168, P_(S)=0, and S=168 are used to define theeffective coding rate of ½ in the encoding block B2. In the encodingblock B2, the effective coding rate is equal to the coding rate,according to this scenario. In another embodiment, to efficientlytransmit a 29-byte MPDU, the parameters N_(L)=64 bits, P_(S)=68, andS=168 are used in the encoding block B1 to define the effective codingrate of (64+36)/(64+36+168)=0.373, and the parameters N_(L)=168,P_(S)=0, and S=168 are used to define the effective coding rate of ½ inthe encoding block B2. Similar to the example scenario above, theeffective coding rate in the encoding block B2 is the same as the codingrate. It each case, the entire MPDU is encoded in two encoding blocks.

FIG. 5A is a diagram of an MPDU 140 of a BFT unit formatted using thetechniques of the present disclosure. The MPDU 140 is generally similarto the prior art MPDU 70 depicted in FIG. 3B. However, unlike the priorart MPDU 70, the MPDU 140 does not include a duration field. In thisembodiment, the MPDU 70 occupies 27 bytes. Thus, if used with a BFTframe in which the first encoding block is formatted similar to thefirst encoding block of the prior art BFT frame 50 (see FIG. 3A), theMPDU 140 can be encoded in only two encoding blocks of length L=336.However, the MPDU 70 can also be used with the BFT frame 120 illustratedin FIG. 4, for example.

Upon receiving the MPDU 140, a receiving device determines theinformation typically specified in the duration field 72 of the priorart MPDU 70 using other information associated with the MPDU 140,according to an embodiment. For example, the receiving device deferschannel access until the corresponding Tx SS sequence completes. Thetime at which the Tx sector sweep sequence completes is in turncalculated using the known duration of the Tx SS frame and the countdownvalue (specified in the CDOWN field of an SS IE, for example).

FIG. 5B is a diagram of an MPDU 150 of a BFT unit formatted usinganother technique of the present disclosure. The MPDU 150 is generallysimilar to the prior art MPDU 70. However, an RA field 152 and a TAfield 154 in the MPDU 150 occupy less than 6 octets each. In someembodiments, each of the fields 152 and 154 stores only a subset of thecorresponding 6-byte address. In an embodiment, each of the fields 152and 154 occupies five bytes or less so that the total length of the MPDU150 is 27 bytes or less. Thus, the MPDU 150 can be used with a BFT framein which the first encoding block is formatted similar to the firstencoding block of the prior art BFT frame 50, or with the BFT frame 120.In some embodiments, the format illustrated in FIG. 5A is used in the“middle” of a sector sweep transmit sequence, and not used in a firstBFT unit transmitted during a sector sweep sequence.

FIG. 5C is a diagram of an MPDU 160 of a BFT unit formatted usinganother technique of the present disclosure. The MPDU 160 is generallysimilar to the prior art MPDU 70. However, the MPDU 160 does not includean RA field or a TA field. Rather, in an embodiment, the MPDU 160includes a six-byte basic service set identifier (BSSID) field 162, aone-byte source association identifier 164, and a one-byte destinationassociation identifier 166. Together, the field 162, 164, and 166 occupyfour bytes less than the fields 73 and 74 of the prior art MPDU 70.Thus, the MPDU 160 can be used with a BFT frame in which the firstencoding block is formatted similar to the first encoding block of theprior art BFT frame 50, or with the BFT frame 120. In an embodiment, theMPDU 160 is used during a sector sweep procedure conducted by a pair ofassociated stations.

FIG. 6A is a diagram of an efficiently formatted sector sweep field 200for use in Tx sector sweep beamforming, for example. The sector sweepfield 200 is generally similar to the prior art Tx SS IE 80 illustratedin FIG. 3C. However, the sector sweep field 200 does not include an IEidentifier field or a length field. According to an embodiment, thesector sweep field 200 is used with a BFT unit in which the presence ofsector sweep field 200 in a certain fixed position is mandatory.Further, according to this embodiment, the sector sweep field 200 alwaysincludes the same set of sub-fields. Thus, a receiving device canproperly process a BFT unit that includes the sector sweep field 200,even though the sector sweep field 200 omits both the IE identifier andthe length. Depending on the embodiment, the sector sweep field 200 isincluded in a Tx SS BFT unit, a SS feedback BFT unit, a SSacknowledgement BFT unit, etc.

Now referring to FIG. 6B, an efficiently formatted sector sweep field210 is generally similar to the prior art Tx SS IE 80, except that asingle field 212 is used to specify either the forward sector selectionor the upper limit to a number of Tx SS BFT units that can betransmitted, depending on the direction in which a BFT unit thatincludes the sector sweep field 210 is transmitted. In particular, whentransmitted in a forward direction, the sector sweep field 210 includesthe information typically transmitted in the field 87 of the Tx SS IE 80and, when transmitted in a reverse direction, the sector sweep field 210includes the information typically transmitted in the field 86 of the TxSS IE 80. In this manner, the size of the sector sweep field 210 isreduced by six bytes relative to the Tx SS IE 80. Thus, in someembodiments, a sector sweep field (or another field of a BFT unit)includes a field or a sub-field that specifies a first parameter typewhen the BFT unit is transmitted in the forward direction, and a secondparameter type when the BFT unit is transmitted in the reversedirection.

Referring to FIG. 6C, an efficiently formatted sector sweep field 220 isgenerally similar to the prior art Tx SS IE 80, except that the sectorsweep field 220 does not include a countdown (CDOWN) field. In anembodiment, the sector sweep IE 220 is used in an SS feedback BFT unitor an SS acknowledgement BFT unit because neither the SS feedback BFTunit nor the SS acknowledgement BFT unit needs the information conveyedin the CDOWN field. However, according to this embodiment, devices donot use the sector sweep IE 220 in a Tx SS BFT unit because the Tx SSBFT unit requires the information conveyed in the CDOWN field.

FIG. 7A is a diagram of a frame control field 230 for use in a BFT unit,formatted using one of the techniques of the present disclosure. Theframe control field 230 consists of a protocol version sub-field 231, atype sub-field 232, and a sub-type sub-field 233. As compared to theprior art frame control field 100 (see FIG. 3D), the frame control field230 omits several fields (e.g., ToDS, FromDS, etc.) that carryinformation not required in a sector sweep beamforming trainingprocedure. Accordingly, the frame control field 230 is eight bitsshorter than the frame control field 100.

In another embodiment, a frame control field 240 has the same length asthe frame control field 100. However, similar to the frame control field230 discussed above, the frame control field 240 omits several fieldsincluded in the prior art frame control field 100, and instead includesa sector sweep IE data field 242 to accommodate a portion of the Tx SSIE.

FIG. 8 is a block diagram of an example efficient BF controller 300 usedin the station 12 and/or the PCP 14, according to an embodiment. Theefficient BF controller 300 implements one or more of the techniquesdiscussed above with reference to FIGS. 4-7B. In an embodiment, theefficient BFT controller 300 includes a beamforming processing unit 302to implement a beamforming procedure (e.g., a Tx sector sweepbeamforming training procedure, an Rx sector sweep beamforming trainingprocedure, a Tx beam refinement procedure, an Rx beam refinementprocedure), a BFT unit generator 304 to generate BFT units for one orseveral of the procedures supported by the beamforming processing unit302 using beamforming data supplied by the beamforming processing unit302, a MAC generator 306 to generate the MAC portion of a BFT unit(e.g., a MAC header), a PHY generator 308 to generate the PHY portion ofthe BFT unit (e.g., PHY preamble, PHY header), and a block encoder 310to generate encoding blocks that include data bits and check bits (or,in some cases, data bits, padding bits, and check bits). In anembodiment, the encoder 310 is an LDPC encoder.

In some embodiments, the MAC generator 306 formats the MPDU portion of aBFT unit according to the format of FIG. 5A, 5B, or 5C. In someembodiments, the MAC generator 306 formats a sector sweep informationelement using one of the formats illustrated in FIGS. 6A-C. Further, insome embodiments, the MAC generator 306 formats a frame control fieldaccording to the format illustrated in FIG. 7A or 7B.

With continued reference to FIG. 8, in some embodiments, the PHYgenerator 308 and/or the encoder 310 format a BFT unit (and, inparticular, the PPDU portion of the BFT unit) according to the formatillustrated in FIG. 4. The BFT unit generator 304 controls the selectionof the PHY format, the MAC format, or both, for a particular procedure(e.g., Tx sector sweep beamforming training, Rx sector sweep beamformingtraining), according to an embodiment. In some situations, the BFT unitgenerator 304 causes the MAC generator 306 and/or the PHY generator 308and the encoder 310 to apply different formats to BFT units depending onwhether the BFT unit is at the beginning of a training sequence or inthe middle of the training sequence.

In some embodiments, two or more of the techniques discussed above arecombined to further reduce the size of a BFT unit, an MPDU, or aninformation element included in the MPDU. Further, the techniquesdiscussed above can be used with any block encoding technique such asLDPC, for example. Although the examples discussed above refer toencoding blocks of size 336 bits, these techniques generally can beapplied to encoding blocks of other sizes.

At least some of the various blocks, operations, and techniquesdescribed above may be implemented utilizing hardware, a processorexecuting firmware instructions, a processor executing softwareinstructions, or any combination thereof. When implemented utilizing aprocessor executing software or firmware instructions, the software orfirmware instructions may be stored in any computer readable memory suchas on a magnetic disk, an optical disk, or other storage medium, in aRAM or ROM or flash memory, processor, hard disk drive, optical diskdrive, tape drive, etc. Likewise, the software or firmware instructionsmay be delivered to a user or a system via any known or desired deliverymethod including, for example, on a computer readable disk or othertransportable computer storage mechanism or via communication media.Communication media typically embodies computer readable instructions,data structures, program modules or other data in a modulated datasignal such as a carrier wave or other transport mechanism. The term“modulated data signal” means a signal that has one or more of itscharacteristics set or changed in such a manner as to encode informationin the signal. By way of example, and not limitation, communicationmedia includes wired media such as a wired network or direct-wiredconnection, and wireless media such as acoustic, radio frequency,infrared and other wireless media. Thus, the software or firmwareinstructions may be delivered to a user or a system via a communicationchannel such as a telephone line, a DSL line, a cable television line, afiber optics line, a wireless communication channel, the Internet, etc.(which are viewed as being the same as or interchangeable with providingsuch software via a transportable storage medium). The software orfirmware instructions may include machine readable instructions that,when executed by the processor, cause the processor to perform variousacts.

When implemented in hardware, the hardware may comprise one or more ofdiscrete components, an integrated circuit, an application-specificintegrated circuit (ASIC), etc.

It will be appreciated that a method for efficiently formatting a BFTunit has been disclosed. According to the disclosed method, a BFT unitis generated that consists of a PHY preamble and an integer number ofencoding blocks (e.g., LDPC blocks), so that only one encoding blockincludes padding bits. Each of the encoding blocks is of the same fixedlength. In other words, beamforming data is distributed among theminimum number of encoding blocks. In an embodiment particularlyapplicable to some communication networks, the number of encoding blocksis two.

Although the foregoing text sets forth a detailed description ofnumerous different embodiments, it should be understood that the scopeof the patent is defined by the words of the claims set forth at the endof this patent. The detailed description is to be construed as exemplaryonly and does not describe every possible embodiment because describingevery possible embodiment would be impractical, if not impossible.Numerous alternative embodiments could be implemented, using eithercurrent technology or technology developed after the filing date of thisdisclosure, which would still fall within the scope of the claims.

What is claimed is:
 1. A method for generating a beamforming training(BFT) unit, the method comprising: generating, at a communicationdevice, a physical layer (PHY) preamble of the BFT unit; generating, atthe communication device, a PHY header of the BFT unit to include PHYdata; generating, at the communication device, a fixed-length payload ofthe BFT unit to include media access control layer (MAC) data, whereinthe MAC data (i) includes a sector sweep (SS) field having a directionsubfield, a countdown subfield, and a sector identifier subfield, and(ii) omits (a) an information element identifier that identifies the SSfield, and (b) a length identifier that specifies a length of the SSfield; and generating, at the communication device, the BFT unit toinclude the PHY preamble, the PHY header and the fixed-length payload.2. The method of claim 1, wherein generating the BFT unit includesgenerating a predetermined number of encoding blocks using the PHY dataand the MAC data.
 3. The method of claim 2, wherein generating thepredetermined number of encoding blocks includes using low-densityparity check (LDPC) coding.
 4. The method of claim 2, wherein generatingthe predetermined number of encoding blocks includes at least one of:(i) using a number of padding bits in a PHY layer of the BFT unit suchthat the PHY data and the MAC data are encoded into only thepredetermined number of encoding blocks, and (ii) generating a MACprotocol data unit (MPDU) having a length such that the PHY data and theMAC data are encoded into only the predetermined number of encodingblocks.
 5. The method of claim 4, wherein generating the MPDU having thelength such that the PHY data and the MAC data are encoded into only thepredetermined number of encoding blocks comprises generating the MPDU ofa length less than 29 bytes.
 6. The method of claim 1, wherein the BFTunit is one of a sector sweep BFT unit, a sector sweep feedback BFTunit, and a sector sweep acknowledgement BFT unit.
 7. An apparatus,comprising: a beamforming controller implemented on one or moreintegrated circuits configured to generate a physical layer (PHY)preamble of a beamforming training (BFT) unit, generate a PHY header ofthe BFT unit to include PHY data, generate a fixed-length payload of theBFT unit to include media access control layer (MAC) data, wherein theMAC data (i) includes a sector sweep (SS) field having a directionsubfield, a countdown subfield, and a sector identifier subfield, and(ii) omits (a) an information element identifier that identifies the SSfield, and (b) a length identifier that specifies a length of the SSfield, and generate the BFT unit to include the PHY preamble, the PHYheader and the fixed-length payload.
 8. The apparatus of claim 7,wherein the one or more integrated circuits are configured to generate apredetermined number of encoding blocks using the PHY data and the MACdata.
 9. The apparatus of claim 7, wherein the one or more integratedcircuits are configured to generate the predetermined number of encodingblocks using low-density parity check (LDPC) coding.
 10. The apparatusof claim 7, wherein the one or more integrated circuits are configuredto generate the predetermined number of encoding blocks at least byperforming at least one of (i) using a number of padding bits in a PHYlayer of the BFT unit such that the PHY data and the MAC data areencoded into only the predetermined number of encoding blocks, and (ii)generating a MAC protocol data unit (MPDU) having a length such that thePHY data and the MAC data are encoded into only the predetermined numberof encoding blocks.
 11. The apparatus of claim 10, wherein the one ofmore integrated circuits are configured to generate the MPDU of a lengthless than 29 bytes.
 12. The apparatus of claim 10, wherein the BFT unitis one of a sector sweep BFT unit, a sector sweep feedback BFT unit, anda sector sweep acknowledgement BFT unit.
 13. A method, comprising:receiving, at a communication device, a beamforming training (BFT) unit,wherein the BFT unit includes (i) a physical layer (PHY) preamble, (ii)a PHY header that includes PHY data, and (iii) a fixed-length payloadthat includes media access control layer (MAC) data, wherein the MACdata (i) includes a sector sweep (SS) field having a direction subfield,a countdown subfield, and a sector identifier subfield, and (ii) omits(a) an information element identifier that identifies the SS field, and(b) a length identifier that specifies a length of the SS field;identifying, at the communication device, the SS field in the BFT unitbased on a predetermined location of the SS field in the BFT unit; andprocessing, at the communication device, the SS field using apredetermined length of the SS field.
 14. The method of claim 13,wherein the BFT unit is one of a sector sweep BFT unit, a sector sweepfeedback BFT unit, and a sector sweep acknowledgement BFT unit.
 15. Themethod of claim 13, further comprising, prior to identifying the SSfield, decoding, at the communication device, a predetermined number ofencoding blocks to retrieve the PHY data and the MAC data from the BFTunit.
 16. The method of claim 15, wherein decoding the predeterminednumber of blocks includes using low-density parity check (LDPC)decoding.
 17. The method of claim 15, wherein the one or more integratedcircuit are configured to decode the predetermined number of blocksusing low-density parity check (LDPC) decoding.
 18. An apparatus,comprising: a beamforming controller implemented on one or moreintegrated circuits configured to receive a beamforming training (BFT)unit from a transmitting device, wherein the BFT unit includes (i) aphysical layer (PHY) preamble, (ii) a PHY header that includes PHY data,and (iii) a fixed-length payload that includes media access controllayer (MAC) data, wherein the MAC data (i) includes a sector sweep (SS)field having a direction subfield, a countdown subfield, and a sectoridentifier subfield, and (ii) omits (a) an information elementidentifier that identifies the SS field, and (b) a length identifierthat specifies a length of the SS field, identify the SS field in theBFT unit based on a predetermined location of the SS field in the BFTunit, and process the SS field using a predetermined length of the SSfield.
 19. The apparatus of claim 18, wherein the BFT unit is one of asector sweep BFT unit, a sector sweep feedback BFT unit, and a sectorsweep acknowledgement BFT unit.
 20. The apparatus of claim 18, whereinthe one or more integrated circuit are further configured to, prior toidentifying the SS field, decode a predetermined number of encodingblocks to retrieve the PHY data and the MAC data from the BFT unit.